Method of making micromechanical components

Abstract

A method of making micromechanical structures from silicon involves cutting a monocrystalline silicon wafer. The orientation of the crystal structure relative to the flat of the wafer is first determined, and this information is taken into account in the subsequent structuring steps.

What is claimed is: 
     
       1. A method of making micromechanical components from silicon by anisotropically etching silicon wafers in a manner suitable to align the components relative to the crystal structure of the silicon, comprising the steps of: taking a single wafer from a plurality of substantially identical wafers made from a rod-shaped unitary silicon crystal and provided with a substantially flat portion of predetermined length in their circumference;   deriving a value characteristic of the orientation of the crystal structure of said single wafer relative to said flat portion; and   applying said value to the remaining wafers of said plurality for the processing thereof.   
     
     
       2. The method of claim 1, wherein said deriving step further includes: placing a mask on a surface of said single wafer, whereby a substantially rectangular area of said surface is exposed with one margin of aid area extending substantially in parallel to said flat portion of said single wafer;   etching a cavity into said surface along the margins of said area; and   measuring the angular deviation of the edge of at least one wall, of said cavity etched below said mask, relative to the adjacent margin of the area.   
     
     
       3. The method of claim 2, wherein said mask is applied to said surface as a layer of silicon nitride with portions thereof subsequentially removed to expose said area. 
     
     
       4. The method of claim 3, wherein a layer of silicon oxide is provided between said surfaces and said layer of silicon nitride. 
     
     
       5. The method of claim 2, wherein the step of applying said value to said remaining wafers further includes: sequentially placing an alignment mask provided with first alignment indicia corresponding to said value on said remaining wafers; and   adjusting the position of said alignment mask on said wafer by aligning said indicia relative to said flat portion.   
     
     
       6. The method of claim 5, wherein said first alignment indicia comprise first and second marks linearly spaced from each other by a distance substantially equal to the length of said flat portion, and wherein   said adjustment step includes:   placing said first and second markers on the ends of said flat portion and rotating at least one of said first and second markers relative to said flat portion into a position corresponding to said angular deviation.   
     
     
       7. The method of claim 6, wherein said first and second markers comprise centering means having on at least one side thereof a plurality of laterally evenly spaced groups of a plurality of vertically arranged lines, said lines corresponding to predetermined increments of said angular deviation, and wherein said adjustment step includes: aligning said centering means with the ends of said flat portion; and   rotating at least one of said first and second markers relative to the flat portion to move one of said lines corresponding to said angular deviation into alignment with said flat portion.   
     
     
       8. The method of claim 7, wherein said step of rotating said at least one marker proceeds from a position in which a predetermined one of said lines in any one of said groups is in alignment with said flat portion.   
     
     
       9. The method of claim 7, wherein said group of lines are spaced from each other by 100 micrometers and wherein   rotating said at least one marker in increments of one of said vertically arranged lines corresponds to an angular increment of 0.05 degrees.   
     
     
       10. The method of claim 9, wherein said aligning step is performed under a microscope having first and second objective lenses respectively positioned over said first and second markers.   
     
     
       11. The method of claim 10, wherein said alignment masks is provided with second alignment indicia and said step of applying said value to said remaining wafers includes photomechanically reproducing said second alignment indicia on the surface of said remaining wafers.